The paper butterfly has always been one of my favourites. I originally made it for #Truelove for Valentine's day, she still has the original on her dressing table :-)
I was delighted, then, to see that Michael42er has made a YouTube video of his Butterfly model out in its natural environment! Nice work Michael!
Aussiemarkvideos has a butterfly video here as well. Thanks Mark!
Michael42er video is here
AussieMark video is here
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The locus is the technical name given to the line that a point traces out as it moves. In mechanisms the locus is often not the shape that you would predict. Changes in variables, such as the lengths of the pieces or the position of hinges can make a big difference to the locus. As part of the forthcoming Cranks Zine I wanted to show the way that the geometry of a box can change the shape of the locus of a push rod. I put together this crank/slider mechanism using split pins as axles. The baseboard has three alternate axle holes 5cm apart. There are a matching set of 5cm spaced holes on the long push rod. Using a pencil or pen I could then trace out the locus.
By pinning the rotating disk to each hole in turn I traced out three three different locii. Orange with the disk at the orange arrow, black at the black arrow and the widest red shape was with the disk fixed at the red arrow. I have then traced these shape into the computer and copied then acoss to the Crank Zine.
These three shapes are created with the disk fixed in the middle hole, the pencil marking out the locus at each of the three holes in the push rod. Interesting stuff!
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Coming soon, a new edition to the Pocket Paper Engineer Zine collection. This time, cranks! A useful mechanism for all sorts of situations. I've completed the content planning and the artwork, the completed zine will be ready soon.
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Your chance to win the Turning Turtle original as used in the website photography. This competition is open to paid members of the website (both standard and members plus)
To enter, simply leave a comment below or send me an email. On the 14th August I'll draw the lucky winner from the hat of doom!
Thanks to everyone who has entered the previous competitions. This is fun isn't it!
...and the winner is...
Congratulations Blakymcblack! Please send me your address and I'll post out the Turtle.
Thank you to everyone for entering!
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...And the winner of the Original Hammerbot is....
Deal! Congratulations Deal, I'll be in touch for your address. Thank you everyone else for entering the competition. There will be a new competition shortly.
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A quick post showing the arms for the tumbling acrobat model in place. There are two stops to limit rotation. The legs will fit in the place indicated, possible with a paper hinge rather than an axle. I have reduced the weights in the tube to three penny coins total weight 12g. I'm still worried that they pick up quite a bit of speed as they roll down the tube. A friend of the web site who has a plastic version of this automata says that his model has ball bearings with baffles to slow down the roll. Not sure if I can do baffles for coins but I'll give it a try.
<------Edit ------->
I put together this coin tube complete with baffles which slows the coin down nicely. Might need to experiment with different angles and heights of the bump but even as is, it stops the coin crashing too hard into the end of the tube.
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We have a weird plug in the bathroom basin. It doesn't lift out of the sink but stays over the plug hole. Press and release it once and the plug hole seals. Press and release it again and it lifts allowing the basin to empty.
Recently the basin has started to take a long time to empty. I reckoned it was probably time to give it a clean out.
The plug assembly came out of the basin easily by unscrewing it revealing this interesting looking unit. I could make it work by pressing in and releasing the brass body to the right of the picture. Squeeze once to shorten the assembly, squeeze again to restore it to full length. Time to take it apart and see how it works.
I unscrewed the grub screw then removed the spring clip which released a steel pin. The pin was approximately 20mm long with both ends bent over at 90°. It was located inside the body in the position of the pink pin in in the picture above.
With those parts removed the main body came apart easily.
This heart shaped groove is, as its shape suggests, at the heart of the mechanism. The pin sits in the groove and controls how the body of the plug moves. To work properly, the pin has to keep moving round the groove in the same direction and not back-track on itself. This is the clever bit. As the pin moves round the groove it falls down little steps, these stop it returning in the direction from whence it came. Neat!
You can see how the pin and groove move in this animation.
I put the plug assembly back together and returned it to the basin where it now works beautifully again. Even #Truelove is pleased with this latest tinkering as the sink is now sparkling clean!
How does this relate to paper engineering? I think it could be a really useful mechanism for a variety for different automata but my first thought was that I could extend the Logic Goat range!
The flip flop is one of the core logic gates used in computer circuits. Apply an input once and it turns on, apply it again and it turns off. The Flip Flop Logic Goat would work in the same way. Just like with the plug mechanism , press the button and it would nod, press it again and it would raise its head. If I could connect a series of them together I could make Goat counting device!
And all that from cleaning the sink. Sometimes cleanliness pays off!
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Friend of the web site, Smelter, has taken delivery of his shiny new credit card sized Raspberry Pi computer. He has it all set up and connected to the internet. As Smelter says,
"When you've a new toy, and you want a web site to visit, where you gonna call?"
Nice one Smelter!
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The turning turtle project is an idea that I've been thinking about for a while. This picture, from the workshop notes blog shows my original plan. I made up a rough prototype at the time but it didn't work as well as I had hoped. The mechanism itself worked but with the speed of turn of the turtle, it was hard to see the leg movement. At the time I thought about gearing the rotation down so that the legs moved up and down at the same speed but the tortoise turned at one quarter revolution per handle turn. It was all getting a bit complicated.
When I made the ninety degree joint I was looking for a character to add to the top of the box and I remembered the Turning Turtle idea. To keep things simple I didn't try moving the legs.
Following up from the anonymous comment in the Turning Turtle project, there are a few ways that the project could be extended using the ninety degree joint as a starting point. Visit the previous blog post and check out the second comment.
Two possibilities that I'll look into (when I've finished the Acrobat project). First picture, like the original idea, the legs are connected to a cam surface via cam followers. Perhaps if I increase the range of leg movements it will work better. The second possibility, fix the body so that it doesn't rotate. Inside the body, rotate a cam surface so that the legs, head and tail waggle up and down frantically.
Thank you anonymous commenter. These look like interesting ideas!
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Turn the handle and, through the magic of the flexible drive shaft, the hapless tortoise spins on her shell. Think of her as a break dancing turtle if you prefer to think happy thoughts.
Members can download the parts for free at the link. Non members can buy the parts for for £2.50. Have fun!
There are three parts sheets for this project. Print out either the colour or mono sheets as you choose. Note that the last colour sheet has colour printed on both sides. Print out one side, flip the paper over and return it to the printer to print out the other side on the back.
Print the parts onto thin card. (230 micron / 67 lb) Score the dotted lines and cut out the holes before carefully cutting out the pieces.
Fit the box strengtheners inside the box, use the picture in the next frame to help show where the box stiffener goes. It should be near the hole but not touching it.
Complete the box as shown
Repeat the process with the box top. The dotted line on the picture shows where the box stiffener sits. Notice that this part has a recessed area.
Fit the base to the box. Stand the box on a flat surface and make sure that the parts are at right angles to each other before the glue dries.
Assemble the two drive shaft ends in the same way. Glue a washer into place as shown. Glue two of the zig zag pieces to adjacent faces on the drive shaft as shown.
Assemble the cuboid that is the drive shaft joiner.
Fold the zig zag pieces over each other alternately so that each piece is folded four times.
Fold up the ends of the zig zag pieces at ninety degrees and trim them off to approx. one centimeter long.
Glue the ends to the drive shaft centre piece.
Repeat the process with the other drive shaft to make this three section flexible drive.
Fit the shaft marked 'Horizontal' into the main body of the box as shown. Fit a second washer to hold it into place.
Repeat the process with the other end of the shaft.
Glue the top of the box into place, make sure that it is square before the glue dries.
Assemble the handle in three steps.
Fold up and glue together the two box sections.
Glue one box section into the other at ninety degrees.
Roll round the long tab and glue it down.
Glue the handle into place on the box. You now have a completed mechanism which you could use as the starting point for your own projects. A spinning helicopter, a dancing couple a break dancing dude...
Carry on from here to add the spinning tortoise.
Assemble the two parts of the shell.
Fold up the legs and glue them at an angle using the grey area as a guide.
Glue the four legs into the body.
Assemble the head and the neck parts.
Glue the head to the neck.
Fit the head and tail into the body and glue them down. A chop stick is a useful aid in this job.
The completed tortoise. Wrong way up.
Complete the model by fitting the tortoise to the box. Turn the handle and watch her spin!
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